Checking of the dimensions of articles



June 5, 1962 w. LAUT ET AL CHECKING oF THE: DIMENsxoNs 0F ARTICLES Filed July 16, 1956 Inventors ftorney United States Patent 3,037,372 CHECKING OF THE DIMENSIONS l? ARTICLES Wilhelm Laut, Floersheim (Main), and Paul Ehrenberg, Ruesselsheim (Main), Germany, assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed July 16, 1956, Ser. No. 598,194 Claims priority, application Germany July 26, 1955 9 Claims. (Cl. 73-37.5)

This invention relates to a method of and apparatus for the checking of the `dimensions of articles.

Known apparatus for successively checking a number of like manufactured articles required to have dimensions falling within certain limits comprises a conduit having an inlet for the admission of air at a constant pressure, an outlet from which air can be directed against the article being checked, and a liquid column pressure indicator connected to the conduit intermediate its inlet and outlet. When this apparatus is used, the escape of air from the outlet is impeded by the particular surface or surfaces of the article against which air is directed; the pressure in the conduit therefore rises, until a steady value is attained which depends on the proximity of the article surfaces to the outlet and is indicated by the posit-ion assumed by the meniscus of the liquid column of the pressure indicator. The scale of the indicator is calibrated against masters and indicates plus and minus deviations in the dimensions of the article being checked from those of the masters.

In the apparatus according to this invention, there is a device which, upon a fall in pressure in the conduit to a predetermined value, operates to restrict the flow of air therethrough.

The apparatus of the invention can be used in the conventional way for successively checking a num-ber of like manufactured articles required to have dimensions falling within certain limits. Its advantage in use is that when one article, having been tested, is disengaged from the apparatus, the meniscus of the liquid column of the pressure indicator is displaced only to a position corresponding to the pressure at which the pressure-responsive device is set to operate, instead of being displaced to the normal full extent, that is, to a position corresponding substantially to the prevailing atmospheric pressure. Hence, when the article next to be tested is engaged with the apparatus, the liquid column meniscus very quickly takes up its indicator position, so that articles can be successively dimensionally checked at a `high rate.

Preferably, the pressure-responsive device is arranged to restrict air ow through the intermediary of a relay; and it is further preferred that restriction occurs through closure of a valve situated in the conduit, as a result of which air can ow to the outlet only by way of a constricted conduit section in parallel with that in which the valve is situated.

The scope of the invention is deiined by the appended claims; and how it can be performed is hereinafter particularly described with reference to the accompanying diagrammatic drawing of an installation including apparatus according to the invention:

A line 12 is connected to a supply of compressed air to admit air under a constant pressure to a detachable jet 14 forming the inlet of a conduit 15. The constant pressure referred to corresponds to the head of water in a container 1t) above the open end 13 of a vertical tube 11. The outlet of conduit 15 is formed by the diametrically opposite jets '2.7, 28 of a detachable gauge Amandrel 24. The mandrel has guide portions 29 to yfacilitate its insertion into the bore 25 of the article y26 whose dimensions (in this instance, the bore diameter Xf) are to be checked.

Connected to the conduit 15, adjacent the jet 14, there is a liquid column pressure indicator 38, the tube -3=9 of which is connected at its lower part 40 to the container 10, which thus serves as a convenient liquid reservoir for the indicator. The scale 41 of the indicator, which has thereon graduations (not shown) corresponding to convenient units, say 10-3 mm., of difference in the dimensions of the article under test, has adjustably secured thereto a pair of pointers `42 and 43, which can be moved so that the distance T between them can be altered to correspond with the limits between which the dimensions to be checked must lie if the article under test is to be acceptable.

lin a section 17 of the conduit 15 there is a valve 19 which can be opened or closed, by means which will be described later, to control the flow of air through the conduit. Another conduit section 18, in parallel with section 17 and joining the same at 16 and 2.1, has a detachable shutter Z0 with a small hole in it of dimensions suitable to `give a desired restriction in air ow under the particular test conditions employed.

(the junction tube 21 is connected at 22 to a rubber tube 23 leading to mandrel l24.

Connected to conduit 15 between pressure indicator 3S and conduit section 1-7 there is a tube 35 connected to a pressure-responsive switch 33 having a diaphragm 34 to whose lower sur-face is secured a contact 36 connected to a circuit 311 containing a battery 32 and a relay 30 adapted to operate valve 19 of conduit section 17. Below diaphragm 34 there is a contact 37, and this also is connected to circuit 31. The distance between contacts 36 and 37 is adjusted before the apparatus is used, in accordance with the test conditions to be employed, so that contact will be -made when the pressure in conduit 15 rises above a value somewhat less than that corresponding to the maximum permissible diameter of bore 25, and will be broken again when the pressure falls below that value. This pressure corresponds to the level y of the liquid column in tube 39 of the pressure indicator 38.

,'Ilhe apparatus operates as follows:

Suppose that the gauge mandrel 24 has been inserted into the bore A2'5 of the article 26, so that air, admitted to jet 14 under a constant pressure, flows through the conduit 15, the open valve 19 in section 17 (contacts 36 and 37 being together), and tube 23, and issues lfrom the jets Z7 and Z8 of gauge mandrel 24 against the bore surfaces of article 26. The meniscus of the Iliquid column in tube 39 will then assume a position, corresponding to the dimensions of bore 25, slightly above pointer 42 if the bore diameter is too large, or between pointers 42 and 43 if the bore ydiameter is within the required limits, or slightly below pointer 43 if the 'bore diameter is too small. The actual position of the meniscus is noted, and the article is accepted or rejected accordingly.

When the article is disengaged from the mandrel, air escapes freely from the mandrel jets 27 and 28, so that the pressure in conduit 15 begins to fall and the meniscus of the liquid of the pressure indicator 38 begins to rise. However, when the pressure in conduit 15 has fallen to the value at which switch 33 is set to operate, the contact 36 secured to the lower surface of diaphragm 34 is lifted from contact 37 and relay 30 acts to close the valve 19 in conduit section 17. Air can then flow to the jets 27 and 28 of mandrel 24 only by way of the constricted conduit section 18 so that the pressure in conduit 15 falls no further and the meniscus of the liquid column of pressure gauge 38 rises no farther than y.

When the mandrel 24 is engaged with the next article 26 to be tested, the escape of air from jets 27 and 26 becomes impeded, and the pressure in conduit 15 therefore rises. As a result, diaphragm 34 of switch 33 is caused to move downwardly, contact 35 touches contact 37, and relay 30 operates to open valve 19. The meniscus of the liquid column of the pressure indicator again takes up a position corresponding to the dimensions of the article under test. However, since it has only a short distance to traverse, this position is taken up very quickly and with practically no oscillation of the liquid column; and since the tube 39 of the pressure indicator is wetted over only a small part of its total surface area, any error arising from the retention of Water droplets on those surfaces of the tube above the meniscus will be very small.

Various modifications, within the scope of the appended claims, may be made to the apparatus described above; for instance, the valve 19 can be of a type which can be operated by relay 30 not for complete closure, but to leave a small hole for the continued passage of air; section 18 and shutter 20 can then be dispensed with.

We claim:

1. Apparatus for checking the dimensions of an article, comprising a conduit having an inlet for the admission of air at a constant pressure and an outlet from which the air can be directed against said article; a pressure indicator connected to the conduit intermediate its inlet and outlet effective to indicate the flow of air therethrough, and a device responsive to a fall in pressure in the conduit to a predetermined minimum value to restrict thereafter the flow of air therethrough at a point downstream of said indicator and thereby maintain a reduced air ilow until the pressure in the conduit exceeds the predetermined minimum value.

2. Apparatus for checking the dimensions of an article, comprising a conduit having an inlet for the admission of air at a constant pressure and an outlet from which the air can be directed against said article; a pressure indicator connected to the conduit intermediate its inlet and outlet; a pressure-responsive switch connected to said conduit; and means in said conduit downstream from said indicator operable by said switch in response to a fall in pressure in the conduit to a predetermined value to restrict the ow of air therethrough to less than some predetermined amount.

3. Apparatus for checking the dimensions of an article, comprising a conduit having an inlet for the admission of air at a constant pressure and an outlet from which the air can be directed against said article; a pressure indicator connected to the conduit intermediate its inlet and outlet; a pressure-responsive switch connected to said conduit; a relay operable by said switch; and means in said conduit downstream from said indicator operable by said switch through said relay in response to a fall in pressure in the conduit to a predetermined value to restrict the ow of air therethrough.

4. Apparatus for checking the dimensions of an article, comprising a conduit having an inlet for the admission of air at a constant pressure and an outlet from which the air can be directed against said article; a liquid column pressure indicator connected to the conduit intermediate its inlet and outlet; a valve situated in said conduit posterior to said indicator; a constricted conduit section in parallel with said valve; and a pressure-responsive switch connected to said conduit and adapted, in response to a fall in pressure in the conduit to a predetermined value,

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to close said valve and restrict the flow of air through said conduit.

5. Apparatus for checking the dimensions of an article, comprising a conduit having an inlet for the admission of air at a constant pressure and an outlet from which the air can be directed against said article; a liquid column pressure indicator connected to the conduit intermediate its inlet and outlet; a valve situated in said conduit posterior to said indicator; a constricted conduit section in parallel with said valve; a pressure-responsive switch connected to said conduit; and a relay operable by said switch in response to a fall in pressure in the conduit to a lpredetermined value to close said valve and restrict the ow of air through said conduit.

6. Apparatus for checking the dimensions of an article comprising a conduit having an inlet for the admission of air at a constant pressure and an outlet from which the air can be directed against the surface of said article, a pressure indicator connected to said conduit intermediate its inlet and outlet and effective to indicate the flow of air therethrough, means responsive to the air flow through said conduit and effective to maintain at least some predetermined minimum pressure in said conduit at said indicator when said air ow is less than some predetermined amount.

7. In apparatus for checking the dimensions of an article, a conduit having an inlet for the admission of air at a constant pressure and an outlet from which the air can be directed against said article, a pressure indicator connected to said conduit intermediate said inlet and outlet, pressure responsive means connected to said conduit intermediate said inlet and outlet, and air flow restriction means connected to said conduit intermediate said pressure indicator and said outlet and adapted to be operated by said pressure responsive means whereby the air ilow in said conduit is restricted to a predetermined amount.

8. Apparatus in accordance with claim 7 wherein said predetermined amount is determined by a leakage path included in said air flow restriction means.

9. Apparatus for checking the dimensions of an article comprising a conduit having an inlet for the admission of air at a relatively constant pressure and an outlet from which the air can be directed against the surface of the article, a pressure indicator connected to the conduit between the inlet and the outlet, and means responsive to the pressure in the conduit, the means being operative when the pressure in the conduit is at a predetermined minimum to maintain a certain minimum air ow through the outlet.

References Cited in the le of this patent UNiTED STATES PATENTS 2,486,052 Moore Oct. 25, 1949 2,560,883 Mennesson July 17, 1951 2,564,527 Fortier Aug. 14, 1951 2,626,464 Mennesson Jan. 27, 1953 2,841,006 Baker July 1, 1958 2,845,791 Loxham et al Aug. 5, 1958 2,845,792 Eisenhardt Aug. 5, 1958 FOREIGN PATENTS 1,027,076 France Feb. 1l, 1953 

